How To Add the gzip Module to Nginx on Ubuntu 14.04

Introduction

How fast a website will load depends on the size of all of the files that have to be downloaded by the browser. Reducing the size of files to be transmitted can make the website not only load faster, but also cheaper to those who have to pay for their bandwidth usage.

gzip is a popular data compression program. You can configure Nginx to use gzip to compress files it serves on the fly. Those files are then decompressed by the browsers that support it upon retrieval with no loss whatsoever, but with the benefit of smaller amount of data being transferred between the web server and browser.

Because of the way compression works in general, but also how gzip works, certain files compress better than others. For example, text files compress very well, often ending up over two times smaller in result. On the other hand, images such as JPEG or PNG files are already compressed by their nature and second compression using gzip yields little or no results. Compressing files use up server resources, so it is best to compress only those files that will reduce its size considerably in result.

In this guide, we'll discuss how to configure Nginx installed on your Ubuntu 14.04 server to utilize gzip compression to reduce the size of content sent to website visitors.

Prerequisites

Step 1 — Creating Test Files

In this step, we will create several test files in the default Nginx directory to text gzip's compression.

To make a decision what kind of file is served over the network, Nginx does not analyze the file contents because it wouldn't be fast enough. Instead, it just looks up the file extension to determine its MIME type, which denotes the purpose of the file.

Because of this behavior, the contents of the test files is irrelevant. By naming the files appropriately, we can trick Nginx into thinking that one entirely empty file is an image and the another, for example, is a stylesheet.

In our configuration, Nginx will not compress very small files, so we're are going to create test files that are exactly 1 kilobyte in size. This will allow us to verify whether Nginx uses compression where it should, compressing one type of files and not doing so with the others.

Create a 1 kilobyte file named test.html in the default Nginx directory using truncate. The extension denotes that it's an HTML page.

sudo truncate -s 1k /usr/share/nginx/html/test.html

Let's create a few more test files in the same manner: one jpg image file, one css stylesheet, and one js JavaScript file.

sudo truncate -s 1k /usr/share/nginx/html/test.jpg

sudo truncate -s 1k /usr/share/nginx/html/test.css

sudo truncate -s 1k /usr/share/nginx/html/test.js

Step 2 — Checking the Default Behavior

The next step is to check how Nginx behaves in respect to compression on a fresh installation with the files we have just created.

Let's check if HTML file named test.html is served with compression. The command requests a file from our Nginx server, and specifies that it is fine to serve gzip compressed content by using an HTTP header (Accept-Encoding: gzip).

In the last line, you can see the Content-Encoding: gzip header. This tells us that gzip compression has been used to send this file. This happened because on Ubuntu 14.04, Nginx has gzip compression enabled automatically after installation with its default settings.

However, by default, Nginx compresses only HTML files. Every other file on a fresh installation will be served uncompressed. To verify that, you can request our test image named test.jpg in the same way.

Step 4 — Verifying the New Configuration

The next step is to check whether changes to the configuration have worked as expected.

We can test this just like we did in step 2, by using curl on each of the test files and examining the output for the Content-Encoding: gzip header.

curl -H "Accept-Encoding: gzip" -I http://localhost/test.html

curl -H "Accept-Encoding: gzip" -I http://localhost/test.jpg

curl -H "Accept-Encoding: gzip" -I http://localhost/test.css

curl -H "Accept-Encoding: gzip" -I http://localhost/test.js

Now only test.jpg, which is an image file, should stay uncompressed. In all other examples, you should be able to find Content-Encoding: gzip header in the output.

If that is the case, you have configured gzip compression in Nginx successfully!

Conclusion

Changing Nginx configuration to fully use gzip compression is easy, but the benefits can be immense. Not only visitors with limited bandwidth will receive the site faster but also Google will be happy about the site loading faster. Speed is gaining traction as an important part of modern web and using gzip is one big step to improve it.